Linear motion rolling guide unit

ABSTRACT

In the linear motion rolling guide unit, because the under seals are removably mounted to the end caps with ease, the under seals are prevented from being deformed or buckled and thus the guide unit does not require high precision machining. The under seals mounted to the end caps have lip portions that seal the gaps between the casing, the end caps and the track rail. A pair of projections provided to each end cap are inserted into an engagement opening formed in and extending longitudinally of the under seal to removably mount the under seal to the end caps with ease. The under seal is allowed to move with respect to the end caps as the under seal is deformed lengthwise and widthwide.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a linear motion rolling guide unitwhich is applied to sliding portions of machine tools, processingequipment, and testing equipment, and in which sliders slide on trackrails with a number of rolling elements interposed therebetween.

Description of the Prior Art

In a conventional linear motion rolling guide unit, when a slider slideson a track rail, the seal between the slider and the track rail isprovided by end seals mounted at both ends of the slider and an underseal mounted to the underside of the slider.

A conventional linear motion rolling guide unit as shown in FIG. 9 hasbeen disclosed. As shown in the figure, the linear motion rolling guideunit consists mainly of a track rail 1 with raceway grooves 9 formedlongitudinally extending on both side walls 11 thereof and a slider 20slidably mounted astride the track rail 1. The slider 20 includes acasing 2, which is slidable relative to the track rail 1 and has racewaygrooves 8 formed at positions facing the raceway grooves 9, a number ofrolling elements or balls 4, which are trapped between the opposingraceway grooves 8, 9 to allow relative motion between the rail and thecasing, and end caps 5 attached to the longitudinal ends of the casing2.

The end cap 5 is fitted with an end seal 19 that provides a seal betweenthe track rail 1 and the slider 20. The casing 2 is provided with anunder seal 3 to seal the casing 2, the longitudinal side walls 11 of thetrack rail 1 and the underside of the casing 2.

The slider 20 is mounted astride the track rail 1 and is freely slidableon the rail 1 because of the presence of a number of balls 4 thatcirculate along the raceway grooves 9 in the rail 1. The balls 4 roll ina raceway 24 formed between the raceway groove 9 in the track rail 1 andthe raceway groove 8 in the casing 2 and are led into a directionchanging passage (indicated by 23 in FIG. 3) formed in the end cap 5 andfurther into a return passage 25 formed parallel to the raceway groove 8in the casing 2, so that the balls 4 roll to circulate in an endlessraceway.

The under seal 3 is simple in shape and thus can be manufactured easily.However, the under seal 3 has the drawback of being easily deformed bypositioning errors of the casing 2 and the track rail 1 forming racewaygrooves 8, 9 therein and by external force because it is formed of athin plate. To describe in more detail, when the slider 20 slides on thetrack rail 1, any temperature variations and swelling by lubricant ofthe under seal 3 will deform the under seal 3 itself degrading itssealing performance.

Further, in the linear motion rolling guide unit the under seal 3 issecured at both ends to the casing 2 made of a metal by screws, so thatwhen the under seal 3 formed of plastic such as synthetic resin soaks uplubricant and swells after a long period of service, it cannot moverelative to the casing 2 and thus will deform. Once the under seal 3deforms, the tight sealing or contact between the underside of thecasing 2 and the upper surface of the under seal 3 fails, or the sealingportion deforms. In the linear motion rolling guide unit, when thesealing contact between the sealing portion and the side surfaces 11 ofthe track rail 1 degrades, the sealing performance, particularly thedust sealing effect, deteriorates.

Among the dust sealing apparatuses used in the linear motion rollingguide unit are those disclosed by Japanese Utility Model Laid-Open No.118317/1991, 121220/1991, 19918/1992, 23818/1992 and 25028/1992.

The under seal device for the linear guide bearing disclosed in theJapanese Utility Model Laid-Open No. 118317/1991 has projections formedat the axial ends of the under seal that extend in the axial directionto fit into engagement openings formed in the bottom surfaces of theside seals. The under seal is easily attached to or detached from theside seals of large strength so as to increase the strength of the underseal.

The under seal device for the linear guide bearing disclosed in theJapanese Utility Model Laid-Open No. 121220/1991 has a two-prongedprojection, at both axial ends of the under seal, projecting toward thebottom surface of the slider whose prongs can open in an invertedV-shape and be resiliently deformed toward each other. The bottomsurface of the slider is formed at each axial end with a vertical hole,in which the two-pronged projection of the under seal fits, and with athrough-hole that pierces through the sleeve portion of the slider in adirection perpendicular to the vertical hole so that one of the prongsengaged in the vertical hole elastically deforms to urge the under sealtoward the side surface of the guide rail, bringing the side edge of theunder seal into sliding contact with the guide rail.

Further, in the dust sealing apparatus for the linear guide apparatusdisclosed in the Japanese Utility Model Laid-Open No. 19918/1992, theend of the under seal, which closes an opening in the lower part of agap between the slider and the guide rail, is inserted between the bentsurface of the side seal and the underside of the end cap to allowone-action removal and mounting of the under seal. The under seal isformed as a rectangular strip almost equal in length to the slider andthe end of the under seal is fitted between the bent surface of the sideseal and the underside of the end cap.

In the dust sealing device for the linear guide apparatus of theJapanese Utility Model Laid-Open No. 23818/1992, the side seal thatseals openings at the front and back of a gap between the slider and theguide rail is inserted into a recessed groove formed at the end of theopening in the end cap.

The dust sealing device for the linear guide apparatus disclosed by theJapanese Utility Model Laid-Open No. 25018/1992 presses the side sealand the under seal against the sealing surface under a predeterminedpressure by spring elasticity instead of the rubber elasticity toprevent early degradation of sealing function caused by the rubberabrasion, absorb greater effects of dimensional errors and enablestable, easy mounting and dismounting of the side seal and under seal.

The under seal devices for the linear guide bearings or the dust sealingdevices for the linear guide apparatuses disclosed in the abovepublications, like the previously mentioned, conventional linear motionrolling guide unit, do not have the construction that permitsdeformation of the under seal in the axial direction and therefore havethe similar problems. That is, the dust sealing member and the end capare generally formed of different materials so that their thermalexpansions caused by temperature variations differ from each other. Whenthe thermal expansion of the dust sealing member becomes larger thanthat of the end cap, the dust sealing member deflects producing a gapbetween it and the rail or the underside of the sleeve, degrading thesealing effect and making it impossible to prevent dust from enteringthe raceway.

SUMMARY OF THE INVENTION

An objective of this invention is to solve the above-mentioned problemsand to provide a linear motion rolling guide unit, which ischaracterized in that the under seals to seal the gaps between the trackrail and the slider are removably mounted to the end caps to absorbchanges in the length and width of the under seals caused by theirthermal expansion variations or their swelling by soaking of lubricantand prevent possible distortion and buckling of the under seals thatwould otherwise result from thermal expansion variations and swelling,thereby securing good sealing performance at all times and enabling easymounting and dismounting of the under seals.

Another objective of this invention is to provide a linear motionrolling guide unit, which comprises:

a track rail having first raceway grooves formed on longitudinallyextending side walls thereof;

a casing slidable relative to the track rail and having second racewaygrooves formed at positions facing the first raceway grooves;

end caps mounted to the longitudinal ends of the casing;

a large number of rolling elements rolling and circulating throughraceways formed between the first raceway grooves and the second racewaygrooves; and

under seals having a first lip portion that can be brought into sealingcontact with the underside of the casing and the end caps and a secondlip portion that can be brought into sealing contact with the side wallsurfaces of the track rail;

wherein the under seals consist of a metallic core member and an elasticsealing member secured to the core member and having the first andsecond lip portions;

wherein the end caps each have pairs of projections protruding from theunderside of the end caps, the projections in each pair being spacedwidthwise, and each projection is formed with a longitudinally extendingengagement portion;

wherein the core member is formed with longitudinally extendingengagement openings, each of which are formed with engagement clawsalong the longitudinal edges thereof; and

wherein the projections are elastically deformed and inserted into theengagement openings until the engagement portions of the projections areengaged by the engagement claws to attach the under seals to the endcaps.

In this linear motion rolling guide unit, since the projectionsprotruding from the underside of the end caps are fitted into theengagement openings formed in the core member of the under seal, theunder seal can be mounted to and dismounted from the end caps veryeasily. Once the positions of the engagement openings in the under sealare set, simply inserting the projections of the end caps into theengagement openings causes the under seal to be automatically positionedand mounted to the end caps, thus eliminating the need to position theunder seal with respect to the end caps.

Since, with the under seal mounted to the end caps, the sealing memberof the under seal can be formed into a structure that covers thesurrounding of the projections, the gaps in the boundary region betweenthe projections and the engagement openings can easily be sealed. Hence,the under seal can seal well the gaps between the track rail, the casingand the end caps, preventing dust from adhering to the sliding surfaces.

In this linear motion rolling guide unit, since the engagement openingsin the core member are longer than the longitudinal lengths of theprojections, the gaps at the longitudinal ends of the engagement openingbetween the engagement opening and the projections are filled by thesealing member.

Further, since the engagement openings in the core member are set longerthan the longitudinal lengths of the projections and the pair ofengagement portions of the projections are held by the engagement clawsof the core member, if the under seal should expand or contract byswelling due to soaking of lubricant or by thermal expansion due totemperature variations, the under seal can move relatively by followingup lengthwise and widthwise deformations thereof because of the looseconnection between the projections and the under seal, preventing thebuckling or distortion of the under seal.

Therefore, the first and second lip portions of the under seal remain insealing contact with the undersides of the casing and the end caps andwith the side walls of the track rail while moving, thus providing goodsealing performance. That is, the sliding surface between the track railand the slider can be sealed in good condition at all times, preventingingress of foreign matters such as dust, dirt or water.

Because the engagement opening is formed longer than the projections inthe longitudinal direction, if there are positional deviations betweenthe engagement openings in the under seal and the projections of the endcaps due to machining errors, the longitudinal deviations or errors caneasily be absorbed by the elastic member, a part of the under seal,filling the gap between the engagement opening and the projections. Thiseliminates the requirement for high precision in machining and thereforereduces the manufacture cost.

Further, since the upper surface of the core member of the under seal isformed with a raised portion that is made of the same material as thatof the sealing member and which is elastically in contact with theunderside of the end caps, the counteractive force of the raised portionpushes the under seal away from the end caps, causing the engagementportions of the projections to elastically engage the engagement clawsof the core member and thereby reliably and firmly positioning the underseal in the vertical direction with respect to the end caps.

Moreover, because the projections provided to the end caps can be madeof a material equivalent to that of the end caps, the projections can beformed integral with the underside of the end caps, permittingsimultaneous forming and reduction in the number of parts andmanufacturing cost.

Alternatively, the projections may be formed as separate structures andsecurely fitted into the insertion holes formed in the underside of theend caps. This allows only the projections to be removed from the endcaps for replacement. That is, when the projections are damaged, thereis no need to replace the entire end cap, reducing the maintenance costand facilitating the service.

Since the under seal is formed as a separate member from the casing, itis possible to cut raceway grooves in the casing easily with highprecision, substantially improving the bearing performance of the linearmotion rolling guide unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a linear motion rolling guide unit as oneembodiment of this invention;

FIG. 2 is a cross section taken along the line A--A of FIG. 1;

FIG. 3 is a schematic view showing a part of an end surface of the endcap;

FIG. 4 is a bottom view showing a part of the underside of the end cap;

FIG. 5 is a cross section of an example of the projection provided atthe underside of the end cap;

FIG. 6 is a schematic top view of the under seal;

FIG. 7 is an enlarged top view showing an essential portion of FIG. 6;

FIG. 8 is a perspective view showing the end cap and the under seal inan exploded condition; and

FIG. 9 is a perspective view showing an example of a conventional linearmotion rolling guide unit.

DETAILED DESCRIPTION OF EMBODIMENTS

Now, by referring to the accompanying drawings, an embodiment of thelinear motion rolling guide unit according to this invention will bedescribed. In FIGS. 1 through 8 components with the same functions asthose of FIG. 9 are assigned like reference numerals.

The linear motion rolling guide unit of this invention has basically thesame construction as the conventional linear motion rolling guide unitshown in FIG. 9 for example. The guide unit is characterized by the wayin which the under seal 13 is mounted.

The linear motion rolling guide unit includes a track rail 1, which hasraceway grooves 9 formed on the longitudinally extending side walls 11like those shown in FIG. 9, and a slider 20, which is slidable relativeto the track rail 1. The slider 20 includes: a casing 2, which isslidable relative to the track rail 1 and has raceway grooves 8 formedat positions facing the raceway grooves 9 as well as return passages 25;a number of rolling elements 4 that circulate rolling in each raceway 24formed between the raceway grooves 8 and the raceway grooves 9; end caps5 mounted at the longitudinal ends of the casing 2 and having directionchanging passages 23; side seals 19 attached to the end surfaces of theend caps 5; and under seals 13 attached to the end caps 5.

The end caps 5 are secured to the end surfaces of the casing 2 byfastenings such as screws passing through mounting holes. On the inside,the end caps 5 have the direction changing passages formed at both sidesfor changing the direction in which the rolling elements 4 travel alongthe sliding surfaces between the casing 2 and the track rail 1. The endcaps 5 also are formed with a recess to accommodate the track rail 1 sothat it straddles the rail.

The under seal 13 consists of a core member 7 made of a metal such assteel and a sealing member 6 made of an elastic material such as rubberand plastics secured to the core member 7. The sealing member 6 has alip portion 14, which is sealingly engageable with the underside of thecasing 2 and the end caps 5, and also another lip portion 15 that cansealingly engage with the side wall surface 11 of the track rail 1.

The under seal 13 further has a raised strip 21 formed of the samematerial as that of the sealing member 6 on the upper surface of thecore member 7. The raised strip 21 is in elastic contact with theunderside of the end caps 5. The counteractive force of the raised strip21 pushes the under seal 13 away from the end caps 5, so that engagementportions 17 of projections 10 provided on each side of the end caps 5elastically engage with engagement claws 16 of the core member 7,thereby vertically positioning the under seal 13 reliably and securelywith respect to the end caps 5.

This linear motion rolling guide unit is characterized by the followingconstruction. That is, the core member 7 of the under seal 13 is formedwith engagement openings 12 into which a pair of downwardly protrudingprojections 10, spaced widthwise and extending longitudinally from theunderside of each end cap 5, are inserted in order to fix the under seal13 to the underside of the end caps 5. The pair of projections 10 may beformed by cutting a slit 22 in a projection portion of the end cap 5 sothat the slit extends longitudinally along the center of the bottom ofthe projection portion. The engagement openings 12 formed in the coremember 7 are longer in the longitudinal direction than the projections10. The gaps between the projections 10 and each engagement opening 12at the longitudinal ends of the opening are filled by the sealing member6 of the under seal 13. Thus, the under seal 13 can be movedlongitudinally relative to the end caps 5 against the elastic force ofthe sealing member 6 that fills the gaps.

The pair of projections 10 can be deformed relative to the end caps 5 byelasticity. Each of the projection 10 has an engagement portion 17protruding widthwise of the end cap. The engagement openings 12 in thecore member 7 have engagement claws 16 formed along their longitudinaledges. When the engagement portions 17 of the projections 10 engage theengagement claws 16 of the core member 7, the under seal 13 is attachedto the end caps 5 and held stationary.

In the linear motion rolling guide unit the projections 10 provided tothe end caps 5 may be formed integral with the lower part of the end cap5. The projections 10 need only have a hardness that permits temporaryfixing by engaging the engagement portions 17 to the engagement claws 16of the core member 7 and which allows relative motion of the under seal13 with respect to the end cap 5 as the under seal 13 is thermallydeformed lengthwise and widthwise. Thus, the projections 10 can be madeof the same material as that of the end cap 5. When the projections 10are formed integral with the lower portion of the end cap 5, they can beformed at the same time and the number of parts and therefore themanufacture cost can be reduced.

Alternatively, as shown in FIG. 5, the projections 10 provided to theend cap 5 may be formed separate from the end cap 5. The projections 10may be formed by cutting a slit 22 in one structural body 10T andsecurely fitted into an insertion hole 18 formed at the bottom of theend cap 5. When the structural body 10T is fabricated separate from theend cap 5, it is possible to use not only the same material but alsodifferent materials for the structural body 10T and the end cap 5.Particularly because the structural body 10T is removable from the endcap 5, there is no need to replace the associated end cap 5 when theprojections 10 are damaged, making maintenance easy.

When the end caps 5 and the projections 10 are formed separately, theprojections 10 may be securely fixed to the end caps 5 by mounting theend caps 5 to the ends of the casing 2, forming the insertion holes 18in the end caps 5 at positions corresponding to the engagement openings12 formed in the core member 7 of the under seal 13, and then insertingthe projections 10 into the insertion holes 18. In this case, variouslengths of the casing 2 can be dealt with.

Another way of fixing together the end caps and the projections involvesforming the projections 10 first integrally with the end caps 5 and,when only certain projections 10 are damaged, removing the projections10, cutting the insertion holes 18 in the end caps 5 where theprojections existed, and securely inserting new projections 10 into theinsertion holes 18.

Since the under seal 13 is removably fitted to the end caps 5 and notrigidly secured to the casing 2, the under seal 13 will not deform orbuckle with respect to the casing 2 and end caps 5 even when there arethermal expansion variations among components caused by temperaturechanges. Therefore, the under seal 13 provides a good sealingperformance, because its lip portion 14 is kept in sealing contact withthe underside of the casing 2 and the end caps 5 and the other lippotion 15 in sealing contact with the wall surface 11 of the rail 1.

I claim:
 1. In a linear motion rolling guide unit comprising:a trackrail having first raceway grooves formed on longitudinally extendingside walls thereof; a casing slidable relative to the track rail andhaving second raceway grooves formed at positions facing the firstraceway grooves, the casing also having return passages formed therein;end caps mounted to the longitudinal ends of the casing, the end capseach having direction changing passages; a large number of rollingelements rolling and circulating through raceways formed between thefirst raceway grooves and the second raceway grooves and through thedirection changing passages and the return passages; and under sealsfitted to the end caps, each of the under seals being made up of ametallic core member and an elastic sealing member secured to the coremember; said linear motion rolling guide unit characterized in: thateach sealing member has a first lip portion that can be brought intosealing contact with the underside of the casing and the end caps and asecond lip portion that can be brought into sealing contact with theside wall surfaces of the track rail; that the end caps each have oneach side a pair of projections protruding from the underside of the endcaps, the projections in each pair being spaced from each otherwidthwise, and each projection is formed with an engagement portion atthe front end thereof; that the under seals are each formed withengagement opening in the core member and the engagement opening has anengagement claw formed at each longitudinal edge portion thereof; andthat the projections are elastically deformed and inserted into theengagement openings until the engagement portions of the projectionsengage the engagement claws to attach the under seals to the end caps.2. A linear motion rolling guide unit as claimed in claim 1,characterized in:that the projections provided to the end caps extendparallel to each other and longitudinally of the end cap and are eachformed at their front ends with an engagement portion that projectswidthwise of the end cap; that the engagement openings formed in thecore member are longer than the longitudinal lengths of the projections;that the core member has the engagement claws formed integral therewiththat extend inwardly from the peripheral portion of the engagementopenings; and that the engagement portions of the projections are heldby the engagement claws of the core members to mount the under seals tothe end caps.
 3. A linear motion rolling guide unit as claimed in claim2, characterized in:that the projections are formed rectangular in crosssection and the engagement portions of the projections extend over theentire length of the longer side of the rectangle on both sides; andthat the engagement openings in the core member are rectangular and theengagement claws are formed over the entire lengths of the longer sidesof each engagement opening on both sides.
 4. A linear motion rollingguide unit as claimed in claim 1, characterized in:that the sealingmember has a raised portion that extends on the upper surface of thecore member and which is made of the same material as that of thesealing member; and that when the under seals are mounted to the endcaps, the raised portions come into elastic contact with the undersideof the end caps thereby vertically positioning the under seals withrespect to the end caps.
 5. A linear motion rolling guide unit asclaimed in claim 1, characterized in:that the projections are formedintegral with the end caps and made of the same material as that of theend caps.
 6. A linear motion rolling guide unit as claimed in claim 1,characterized in:that the projections are formed separate from the endcaps and securely fitted into insertion holes formed in the end caps.